1. Field of the Invention
The present invention relates to a glass ceramic composition capable of being fired at a low temperature with an extremely low permittivity and a sufficient strength and to a coil electronic component having the glass ceramic composition.
2. Description of the Related Art
In accordance with higher frequency of communication devices including mobile phones, a number of ceramic coils corresponding to a high frequency of 1 GHz or higher have been employed for a transmission part and a reception part of the communication devices. In particular, these ceramic coils are required to have a low permittivity for correspondence to high frequency, and a low temperature sintering of 950° C. or lower is essential for applying Ag or Ag alloy with a low resistance and a low loss to an internal conductor.
Thus, a glass-based material with a low permittivity is widely and typically used as a material of the ceramic coils. However, a glass-based material has the following problem: when a glass-based material is used as an element body of a coil electronic component including a ceramic coil, a much lower strength than originally expected is just demonstrated due to cracks originated from flaws, dents, and the like generated on a surface of the element body.
To solve the problem, Patent Document 1 and Patent Document 2 propose techniques for improving a mechanical strength of a glass-based material itself. Although a sufficient mechanical strength can be ensured in using the glass-based material of Patent Document 1 as an element body of a coil electronic component, the glass-based material of Patent Document 1 has the following problem: it is essential to preliminarily calcine a raw material and thus a process load is large due to complexity of manufacturing processes for obtaining ceramic powder with a particle size distribution applicable to multilayer components. Although a mechanical strength can be also ensured in using the glass-based material of Patent Document 2 as an element body, the glass-based material of Patent Document 2 has the following problem: a Q value in a high frequency region is decreased because internal electric layers become uneven due to generation of many crystal particles after being fired.
From another point of view, Patent Document 3 proposes a technique for improving a mechanical strength of a coil electronic component as a whole by sandwiching top and bottom of a coil portion by a glass-based material with a high shape retainability. Such a technique allows shape retention layers to be placed on top and bottom of the coil portion so as to ensure its strength. It is thus possible to use a glass-based material for the internal coil portion that is not necessary to care about strength and favorable for heightening Q values and has the small number of crystal particles and a low relative permittivity. However, a glass-based material with a high strength used for shape retention layers has a relative permittivity that is higher than that of a glass-based material used for a coil portion, and there is thus a problem that a Q value of a coil electronic component as a whole is decreased no matter how selectively a glass-based material that is easy to heighten a Q value is used for the coil portion.
Patent Document 1: Japanese Patent No. 4239534
Patent Document 2: Japanese Unexamined Patent Application Publication No. 2005-15239
Patent Document 3: Japanese Unexamined Patent Application Publication No. 2013-58538